1. Field of the Invention
The present invention relates to a magnetic recording medium prepared by using a metallic powder as a magnetic powder and the preparation thereof. More particularly, it relates to a magnetic recording medium prepared by using a metallic magnetic powder having improved dispersibility and oxidation resistance and the preparation thereof.
2. Description of the Prior Arts
Recently, it has been common to use a magnetic recording medium prepared by coating a magnetic composition as a mixture of a magnetic powder and a binder resin on a film made of polyacetate, polyvinyl chloride or polyester as a substrate. Thus, if a metallic magnetic powder made of iron and cobalt is used as the magnetic powder, high mutual action is easily resulted between particles to cause coagulation of the particles and to prevent uniform dispersion of the particles in the binder resin because the metallic powder has remarkably larger magnetic moment in comparison with the oxide type magnetic powder such as iron oxide and chromium oxide which have been mainly used. Therefore, the metallic magnetic powder disadvantageously has not satisfactory electromagnetic characteristics and physical characteristics such as powder falling inhibition which are required for the magnetic recording medium. Moreover, the metallic magnetic powder has inferior oxidation resistance whereby the magnetic recording medium prepared by using such magnetic powder disadvantageously causes magnetic deterioration in ageing caused by the oxidation.
Various improvements have been considered to improve the dispersibility and the oxidation resistance of the metallic magnetic powder, however, no satisfactory result has been attained. For example, the metallic magnetic powder coated with a silane compound has excellent oxidation resistance, but has inferior dispersibility whereby the electromagnetic transfer characteristic is disadvantageously inferior. When the metallic magnetic powder is treated with oleic acid, the dispersibility is satisfactorily improved, but the oxidation resistance is not satisfactory.